What happened
On 18 June 2015, a Singapore Airlines Airbus A380-800, registration 9V-SKI, was performing a scheduled flight from Hong Kong to Singapore. During the descent phase, specifically between 7,000 and 3,000 feet, the flight crew observed isolated cumulus clouds. To avoid these clouds, the pilot flying executed a parallel track deviation of approximately 3 to 4 nm.
As the aircraft passed the clouds, it encountered a brief period of turbulence lasting about two seconds. While the flight crew noted the event, they were unaware that the motion had caused three cabin crew members to fall in the upper deck aft galley. One crew member sustained a serious injury involving a fracture to the right foot, while two others sustained minor injuries to their limbs.
The investigation
The investigation examined the flight path, weather radar data, and the crew's response to the weather conditions. Investigators analyzed the weather radar returns, which showed that while the crew perceived no significant weather, a wet turbulence area had been present within a 30 nm radius of the aircraft during the descent.
Additionally, the investigation looked into the preservation of flight data. Because the flight crew did not initially realize the severity of the crew injuries, they did not request the removal of the flight recorders. Consequently, while the Flight Data Recorder (FDR) was successfully retrieved, the Cockpit Voice Recorder (CVR) had been overwritten and was unavailable for analysis.
Findings
- The flight crew's decision to fly through clear spaces between clouds rather than a wider deviation was insufficient to avoid the turbulence.
- The crew did not notice the magenta-colored indicators on the navigation displays that signify a wet turbulence area.
- The lack of a prompt request to preserve the CVR led to the loss of critical cockpit audio data.
Safety action
Following the investigation, the operator issued a Flight Operations Notice in September 2016. This notice served to share lessons learned and reinforced the requirement for crews to log technical entries for recorder removal whenever turbulence results in injuries that render a crew member unfit for duty.